The effects of nematic order on the electronic structure of FeSe and NaFeAs

Date

Sep 25, 2017

Time

3:00 PM - 4:00 PM

Speaker

Dr. Matthew Watson

Affiliation

Diamond Light Source, United Kingdom

Language

en

Main Topic

Materialien

Other Topics

Materialien, Physik

Host

Christine Malbrich

Description

Abstract The appearance of high-temperature superconductivity in the Fe-based superconductors is likely to be linked to the variety of other ordered states found in their phase diagrams. Certain systems, including FeSe, exhibit an unusual `nematic' phase where fourfold symmetry of the lattice is spontaneously broken without magnetic order. Angle-resolved photoemission spectroscopy (ARPES) measurements of FeSe are able to give a unique insight into the evolution of the electronic structure in the nematic phase. Previous ARPES measurements have revealed substantial shifts of both the electron and hole bands associated with the onset of the nematic order parameter, however the interpretation of these data has caused some controversy. One particularly important issue has been the role played by the formation of twin orthorhombic domains in samples. Here I will argue that our high-resolution ARPES results obtained on twinned samples [1,2] point uniquely towards a “unidirectional nematic bond ordering”. I will additionally present ARPES results on ``detwinned” FeSe crystals [3], revealing remarkable anisotropies which are hidden in measurements of twinned samples. Finally I will show new ARPES results on detwinned NaFeAs samples, and discuss what aspects of the electronic structure may be characteristic of nematic order. [1] “Evidence for unidirectional nematic bond ordering in FeSe” M. D. Watson et. al., Phys. Rev. B 94, 201107(R) (2016) [2] “Shifts and Splittings of the Hole Bands in the Nematic Phase of FeSe” M. D. Watson et. al., J. Phys. Soc. Jpn. 86, 053703 (2017) [3] M. D. Watson et. al., arXiv:1705.02286 (2017)

Links

• Seminars at the IFW

Last modified: Sep 25, 2017, 10:00:59 AM